Blows ignition fuse when put into gear

[natemoen]

I did explain it; if you can't understand the explanation, I can't help you....

So you are saying once the bike is taken out of neutral the light circuit can no longer ground through the neutral switch and due to the short it is then able to ground through the tci which then gets overloaded and blows the fuse?

[cywelchjr]

So you are saying once the bike is taken out of neutral the light circuit can no longer ground through the neutral switch and due to the short it is then able to ground through the tci which then gets overloaded and blows the fuse?

I don't understand it either, and I TEACH electronics (ok, so I DID teach electronics in the past). Electrons ALWAYS take the easiest path to ground, which would be the short, never that which draws less current. The problem that causes the bikes to die when taken out of neutral when water is in the wiring harness and in those splices is because of cross talk between the wires and from the light circuit that hides the signals that the ground from the switch hides. The bulb does NOT provide the ground, the ground is provided by the switch, the bulb provides the HOT line, so taking the bulb out would remove the voltage source to down there. So, for that to be causing the fuse to blow, the light would have to be shorted, and it would blow when OUT of gear, not in gear. So Steve's understanding of electrical in this case as is often the case is backwards.

I too would suggest disconnecting the neutral switch, it's far easier than removing the bulb, and makes a good first test, as either the problem goes away, the fuse blows immediately, or nothing changes in which case the problem is just a coincidence with that. Being an 81 there is other stuff involved, as there are also interlocks that are not involved in the earlier models. I'm not sure if they could cause this problem as I have not looked at the 81 diagrams lately, but they could, and removing the neutral switch will at least tell if that's the problem. If it makes the fuse blow right away, then the light can be removed to kill the hot part of the circuit but the switch most likely need not be reconnected at least until the problem has been found.

[bikerphil]

If your bike has clutch/sidestand interlocks, it will have relays that can be bypassed. IIRC, some 81's have those safety features or was it 82.

[crazy steve]

So Steve's understanding of electrical in this case as is often the case is backwards..

Cy, you're as bad as Greg....

I never said the short was to ground; I said that the wire to the neutral switch was shorting to one of the pick-up coil circuits. Re-read post 27...

The TCI amplifier takes the millivolt/amp signal from the pickup coil and boosts it up to switch the ignition coil. If the neutral light doesn't have a path to ground through the neutral switch, it will seek another path, in this case through the pick-up coil wiring; if it were shorted to ground, the light wouldn't go off. So you've now upped the input to the amplifier, which will still try to amplify it by however much gain is built into it. This will cause the amp to draw more power, thereby blowing the supply fuse to the TCI. Remember, the wire from the neutral light will have 12 volts on it. If any of you can come up with a better explanation of how the neutral switch is taking out the ignition fuse, I'm ready to hear it....

[crazy steve]

So you are saying once the bike is taken out of neutral the light circuit can no longer ground through the neutral switch and due to the short it is then able to ground through the tci which then gets overloaded and blows the fuse?

Yes.........

[petejw]

without adding any further confusion, if the blue nuetral wire was shorting out wouldnt the neutral light stay on with the ignition on (engine not running) but with the bike in any gear?

[natemoen]

without adding any further confusion, if the blue nuetral wire was shorting out wouldnt the neutral light stay on with the ignition on (engine not running) but with the bike in any gear?

Wouldn't that still blow the fuse though under this theory?

[crazy steve]

Pete, if it were shorting to ground, yes. But if it were shorted to another circuit, the light would seek a ground path through that circuit.

Here's what I see happening...

The neutral lamp is 3.4 watts, which calculates out to .28 amp. When the neutral switch is closed, you have basically zero resistance to ground through the switch. So if the neutral wire is shorted to a pick-up coil circuit (which is 720 ohms), the current through the switch when it's closed is .28 amp less roughly .00028 amp which 'leaks' into the higher-resistance pick-up circuit. This is below the threshold of what the amplifier senses, so the bike starts/runs no problem. We're dealing with a parallel circuit at this point.

Open the switch (shift the bike out of neutral). The current can no longer go to ground through the switch, so it takes the 'alternate' path. But now it's a series circuit, so the full .28 amp goes the the TCI. This is a much higher current than what the reluctor generates, and the amplifier attempts to boost it. It draws much more input power and blows the fuse. So just disconnecting the neutral switch will mean that you'll blow the ignition fuse as soon as you turn the key. Removing the lamp will disconnect power at the lamp, and the neutral wire running with the pick-up coil wires is now dead as it's not connected at either end; the bike will start/run and go down the road, just no neutral light.

That clear?

[cywelchjr]

Cy, you're as bad as Greg....

I never said the short was to ground; I said that the wire to the neutral switch was shorting to one of the pick-up coil circuits. Re-read post 27...

The TCI amplifier takes the millivolt/amp signal from the pickup coil and boosts it up to switch the ignition coil. If the neutral light doesn't have a path to ground through the neutral switch, it will seek another path, in this case through the pick-up coil wiring; if it were shorted to ground, the light wouldn't go off. So you've now upped the input to the amplifier, which will still try to amplify it by however much gain is built into it. This will cause the amp to draw more power, thereby blowing the supply fuse to the TCI. Remember, the wire from the neutral light will have 12 volts on it. If any of you can come up with a better explanation of how the neutral switch is taking out the ignition fuse, I'm ready to hear it....

Buzz, sorry, incorrect electronics theory again. The TCI doesn't amplify the pickup coil signal, the pickup coil signal is used to switch power transistors on and off, how much input comes in is not going to make a difference, so you're wrong again. This is a case of trying to theorize without the background in the theory to do so, the circuit in question just doesn't work that way. And just because you don't want to listen to what the guy who has worked in electronics since 1976 (that doesn't count my hobby years before I graduated from high school, just the formal electronic schooling and working years) then so be it. But please don't try to make up new theories of electronics on the fly? Since there are multiple OTHER circuits on an 81 that are not on the other years having to do with the starter interlock that earlier models don't have, there are other circuits brought into the line having nothing to do with the ignition circuit that could cause the fuse to blow, and it's likely one of those, most likely the starter interlock system that only the 81 and XJ have.

[crazy steve]

...The TCI doesn't amplify the pickup coil signal...

So the factory service manual is wrong? That's funny, I could have sworn it said the signal from the pick-up coils is amplified.... Oh wait, it does say that... page 6-8.

What's the problem? Everyone is putting the problem off on un-named 'other' circuits, none of which have any connection to the TCI. As you pointed out, the interlock circuits are for the starter, and have nothing to do with the ignition. You don't even have the connection to the ballast resistor, as that's gone on the '81s. So far, I'm the only one with an explanation that fits the facts; people say I'm wrong, but can't explain why or the problem...

I'm not inventing any new theory here Cy; this is the same old stuff. I just seem to have a bit better grasp on it....

The funny part is this is exceedingly easy to check; pull the lamp, and if the problem goes away, that's it....

[DAVINCI]

See post #2

[BA80]

Cy, you're as bad as Greg......

Ok, Steve is right and everyone else is wrong. I guess I'll take my bad self out of this p!ssin' contest.

Good luck David. PM me if you've got any questions.

[DGXSER]

Wow, when did this become a contest or some election of some kind. Why does one persons suggestion have to be wrong just because you do not agree with it. You may feel it will not yeild the results, which a couple folks OBVIOUSLY DO, ok, then say so and be done why go on and on and on and on about it I have seen some really crazy things end up being the problem before. Steve is just delving very deep into electrical theory, and although it may be fairly improbible, it is not impossible. So instead turning this thread into a debate over how Steve is wrong, lets try being positive and helping David solve his problems by adding more ideas of what it could be.

Phil, the sidestand interlock is an XJ only thing, stock anyway. (I have thought of adding one to mine). The clutch interlock is on my current 81, although it was inactive on my previous SH, and it does not show up at all on the wiring diagram for an SH. At least the clutch interlock could definitley be a good theory. And if a PO added a sidestand interlock, it could be the issue as well.

Looking over the ignition circuits powered by the fuse that keeps blowing, that Red/White wire feeds power to the right handle bar E-stop switch, if it is in the on position, it feeds power to the starter solenoid, and the TCI. The TCI then powers the coils, and the pickup coils.

So, you have to be drawing more power through that fuse than the rated ten amps when you put it in gear. So somethign is causing a dead ground in one of those wires. If it were me, I pull the seat and get a bunch of fuses and start metering wires till you find where it is getting the high draw from.

An easy wyy to eliminate the neutral switch is to open your headlight bucket, find the connector to your tach and pull it. The tan wire feeding the tach powers the neutral switch. If you pull that connector, start the bike and put it in gear and it stays running, or if it still dies, you will know if that is the problem.

That not being the problem, then all I can think is a short that only shows under load or a wire that gets jarred when the bike goes into gear.

[cywelchjr]

See post #2

Yes Randy, that's a good area to check. My point is that to get the current flow Steve is talking about through the TCI, would require smoking the TCI, so it would happen exactly once, and the bike wouldn't run afterwards. While biasing the power transistors might push them further into the saturation zone, the limiting factor for current here is the COILS not the TCI.

That said, I'm done arguing. I've got too many other things that I have to deal with that actually have impact on my life. I'll finish up my writup on the 2 prong flasher mod, and I'll post it here and on .org, and then I'm washing my hands of this place. I don't need the stress and increased blood pressure. Once that's posted, I'll be available to answer questions about the mod over on .org, I probably won't be actively over on here anymore.

[fredintoon]

I am back to working on the wiring on the bike. I know the wiring for the starter button is not working. I can jump the solenoid and get the bike started. With the engine running and the green neutral light on, I shift into first gear let out the clutch and the ignition fuse blows in the engine dies.

With the engine running and the green neutral light on, I can start shifting up through the gears and ignition fuse blows and the engine dies.

David

Hi Guys,
all this trash talk ain't getting David back on the road, eh?
WTF do you think you are? .Org?
Dave,
you got current flowing where it shouldn't.
There's no quickie answer here. You just gotta check out every switch, connection, component and wire until you find the problem.